The present invention relates to a scroll type compressor for a vehicle air conditioner.
A motor-driven scroll type compressor for a vehicle air conditioner has a fixed scroll member and a movable scroll member. The fixed scroll member has a scroll wall and a base plate fixed to the housing of the scroll type compressor, and the movable scroll member has a scroll wall and a base plate engaged with the scroll wall of the fixed scroll member. In operation of the scroll type compressor when the movable scroll member is driven by the electric motor to make an orbital motion, the compression chamber formed between the scroll walls of the fixed and movable scroll members is moved toward the center of the scroll walls while reducing its volume for compression of refrigerant.
In the motor-driven scroll type compressor according to the background art disclosed in Japanese Patent Application Publication No. 2004-301090, a back-pressure chamber is formed in the housing behind the base plate of the movable scroll member and also between the movable scroll member and a shaft support member. The back-pressure chamber is in communication with a first oil reservoir formed in the discharge chamber through a pressure oil supply passage. A second oil reservoir is formed in the suction chamber at the outer periphery thereof. The back-pressure chamber is in communication with the second oil reservoir through an oil extraction passage having therein a regulating valve. An oil return passage is formed in the base plate of the fixed scroll member for connecting the second oil reservoir to the suction chamber formed in the housing on the outer peripheral side of the scroll walls or on the rear side. A gas return passage is formed in the housing for connecting the upper region of the second oil reservoir to the upper region of the suction chamber.
The regulating valve is operable to open and close in accordance with the pressure in the back-pressure chamber, and high-pressure refrigerant gas and lubricating oil are introduced into the second oil reservoir from the back-pressure chamber through the oil extraction passage. The lubricating oil in the second oil reservoir is introduced into the suction chamber through the oil return passage to lubricate sliding surfaces of the compressor. Refrigerant gas separated from the lubricating oil in the second oil reservoir is introduced into the suction chamber through the gas return passage.
According to the background art disclosed in the above Publication, when the amount of the lubricating oil reserved in the second oil reservoir is increased, there arises a problem that the lubricating oil may overflow from the second oil reservoir. In order to solve the above problem, there has been proposed a compressor having a flow passage connecting the oil reservoir to the suction chamber so that any excess lubricating oil in the oil reservoir is returned to the suction chamber through this flow passage when the level of the lubricating oil in the oil reservoir becomes higher than a predetermined level. In this compressor, the flow passage is formed in the oil reservoir at a position higher than the oil return passage. Thus, when the level of lubricating oil in the oil reservoir exceeds the level of the flow passage, excess lubricating oil is introduced into the suction chamber through the flow passage, thus the amount of lubricating oil to be reserved in the reservoir being adjustable so as to maintain a predetermined amount.
According to the above background art, high-pressure refrigerant gas and lubricating oil introduced into the oil reservoir from the back-pressure chamber through the oil extraction passage are dispersed therearound by strong jetting force. A part of the dispersed lubricating oil is directly flowed into the flow passage with refrigerant gas, and then introduced into the suction chamber. As a result, only a small amount of lubricating oil is collected in the oil reservoir and, therefore, the oil rate of the refrigerant circuit, i.e. the circulation efficiency of the lubricating oil in the refrigerant circuit, may be increased. This causes an increase of pressure loss and a reduction of heat exchanging efficiency, with the result that the system performance of the compressor deteriorates.
The present invention is directed to providing a scroll type compressor which prevents lubricating oil flowed from the back-pressure chamber to the oil reservoir through the oil extraction passage from flowing directly into the flow passage.